Fixed between the grip section and a metal knob at the other end of the barrel, this system uses a flexible metal pressure bar. When pressing the knob, the bar is bent and presses the sac.
The hole, neccessary to reach the pen sac is positioned at the barrels end and furthermore closed by a blind cap.
This way, the risk of soiling the clothes in the event of a rotten pen sac was eliminated. This system was as successfull as the leverfiller.